1. Field of the Invention
The present invention relates to a flexible circuit board with an electronic component mounted thereon and an electronic device including the same.
2. Description of Related Art
Conventional circuit boards of this type are described in, for example, International Publication Pamphlet Nos. WO2010/103901 and WO2010/131524. The circuit board described in International Publication Pamphlet No. WO2010/103901 includes a body formed by laminating board sheets made of a flexible material. The body has a mounting area in which electronic components are mounted. In addition, the body has attachment areas intended to contact attachment members provided on an electronic device, and the attachment areas are more deformable than the mounting area. Furthermore, the body is provided with ground conductors. In one specific example of the ground conductors, the ground conductor is essentially opposite to the mounting area with at least one layer of board sheet positioned therebetween, and has a relatively large size.
Furthermore, the circuit board described in International Publication Pamphlet No. WO2010/131524 includes a body formed by laminating a plurality of insulator layers made of a flexible material. The body includes a first board section and a second board section less deformable than the first board section. The first board section is provided with coil conductors for constituting an antenna coil. The second board section has wiring conductors electrically connected to the antenna coil, and also has an electronic component (typically, an integrated circuit) electrically connected to the wiring conductors. The body is also provided with a ground conductor. The ground conductor is a relatively large-sized conductor formed between two insulator layers that are adjacent to each other in the direction of lamination.
Incidentally, various components and modules are integrated in high density within the housing of an electronic device (typically, a smartphone). Accordingly, to place the circuit board 501 in such a housing, in some cases, the circuit board 501 is structured three-dimensionally, as shown in FIG. 7. More specifically, the circuit board 501 has cuts 502a and 502b, which are made where necessary before the circuit board 501 is bent at predetermined positions 503a and 503b in accordance with a spatial shape in which it is to be placed.
However, the circuit board 501 has ground conductors 504a, 504b, and 504c occupying large areas thereof, as described above. The ground conductor 504c is positioned next to the ground conductor 504b with the cut 502b provided therebetween. The ground conductor 504b is a ground conductor positioned in an area where the circuit board 501 is not bent. As in the case of the circuit board 501, the ground conductors 504b and 504c are bent after they are cut. As a result, in some cases, the ground conductors 504b and 504c have a slit portion 505b provided therebetween so as to correspond to the cut 502b. Moreover, the ground conductor 504a is positioned next to the ground conductor 504b with the cut 502a provided therebetween. The ground conductor 504a is cut and bent, so that a slit portion 505a corresponding to the cut 502a is provided between the ground conductors 504a and 504b. 
The slit portions 505a and 505b act like slots in a slot antenna during the operation of the electronic device, depending on their shape and size, resulting in problems such as noise radiation and exogenous noise reception.